According to Carleton, zoledronic acid also "increases the risk of osteonecrosis of the jaw," a severe bone disease. The condition "can be very painful, and is a complication for which there is no good treatment," she added.

So the researchers behind the new study wondered if the drug might be administered less often.

The study was led by Dr. Andrew Himelstein of the Helen F. Graham Cancer Center & Research Institute in Newark, Del. His team randomly gave the drug on different schedules to more than 1,800 patients with breast cancer, prostate cancer, or multiple myeloma that had spread to the bone.

Half of the patients received the drug just once every three months, while the other half received it once per month, all over a two-year period.

After the two years, 795 patients were left in the study. Bone-related problems appeared in 30 percent of those who took the drug once per month and 29 percent of those who took it once every three months, Himelstein's group reported.

Levels of side effects weren't significantly different in the two groups, the findings showed.

That could be good news for cancer patients, said Carleton, who reviewed the new findings but wasn't involved in the study.

"In cancer care, we are always looking to see when we should do more and be more aggressive in our treatment, and when we can do less and possibly decrease complications from treatment," she said.

The new findings may mean "that clinicians can consider decreasing the frequency of giving this medication," Carleton said. And that should mean "fewer treatment visits for the patient and lower costs for cancer treatment," she added.

The finding were published Jan. 3 in the Journal of the American Medical Association.